Method of supporting horizontal heater tubes fired from both sides



Feb. 7, 1967 E KLEIN 3,302,621

METHOD OF SUPPORTIbiG HORIZONTAL HEATER TUBES FIRED FROM BOTH SIDES Filed May 27, 1965 2 Sheets-Sheet 1 INVENTOR BY mam/K hi4 ATTORNEY Feb. 7, 1967 E. KLEIN 3,302,621

METHOD OF SUPPORTING HORIZONTAL HEATER TUBES FIRED FROM BOTH SIDES Filed May 27, 1965 2 Sheets-Sheet 2 INVENTOR Zrz'c 1f Z6272;

ATTORNEY United States Patent METHOD OF SUPPORTING HORIZONTAL HEATER TUBES FIRED FROM BOTH SIDES Eric Klein, Verona, N.J., assignor to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Filed May 27, 1965, Ser. No. 459,351 4 Claims. (Cl. 122-510) The present invention relates to furnaces for heating fluids flowing through tubes which are located within the furnace chamber.

Commonly in tube-heating furnaces the tubes extend longitudinally through the central portion of an elongated furnace the burners being located in the side walls of the furnace on both sides of the tubes. Prolonged exposure to the high temperatures generated in the furnace chamber causes the tubes to sag or become distorted necessitating the presence of tube support structures spaced along the length of the tubes. This is conventionally accomplished by providing pairs of steel columns located within the furnace the Columns having slots therein through which the horizontal tubes are disposed. To allow for expansion of the tubes when the furnace temperature is raised to normal operating temperature the slots in the columns are so arranged that when cold the column does not support the tubes but picks up the load on the tubes as normal operating temperatures are achieved. The result is that the tubes at any other times than at normal operating temperature are not adequately supported.

A further disadvantage of the conventional tube furnace is that the support columns, which must be made from steel alloys which are quite expensive, are subjected because of the heat to oxidizing, cracking, and bending requiring frequent replacement. Not only are the support columns expensive to replace because of the high-cost alloys used, but further financial loss in the form of lost production is assumed by the furnace operator during the period of time the furnace must be shut down for repairs.

A number of improvement-s in tube supports have been devised and used in recent years with only limited success. One improvement commonly used is a support column located centrally in the furnace with lateral support elements afiixed to the column, each element being designed to support an individual or a pair of tubes. With this arrangement certain economies are introduced since it is cheaper to frequently replace only the lateral support elements, but the arrangement still requires the use of high-priced steel alloy support columns which must be replaced less frequently.

Another known improvement is the use of tubular support columns located centrally in the furnace and having lateral support elements secured thereto for supporting the horizontal tubes. The tubular support columns are cooled during operation of the furnace by water being circulated through the supports. Though this arrangement admittedly does prolong the life of the support structure to some extent, t is less than completely satisfactory since eventually tne exterior exposed surfaces of the tubular support columns deteriorate to the point that replacement is inevitably necessary.

It is an object of the present invention to provide a means for supporting tubes centrally located in a furnace which means will not deteriorate after the furnace has been operating at high temperatures for a prolonged period of time.

It is a further object of the present invention to provide a tube-heating furnace in which the support columns for supporting the tubes may be located elsewhere than in the central portion of the furnace chamber.

A still further object of the invention is to provide a furnace for heating tubes in which the support columns for the tubes are not exposed to the high temperatures present in the central portion of the furnace.

Another object of the invention is to provide a furnace for heating tubes in which the support columns support the tubes at all times, irrespective of the temperature of the furnace.

These and other objects and advantages of the present invention will appear more clearly from the following specification in connection with the accompanying drawings in which:

FIGURE 1 is a section through a tube-heating furnace showing in part the design of the furnace and the support means for the tubes;

FIGURE 2 is a plan view of the furnace shown in FIGURE 1 taken on the line IIII;

FIGURE 3 is an enlarged plan view of a portion of the furnace wall showing the tube support elements and a column in greater detail; and

FIGURE 4 is a detailed side view of the support elements and column taken along the line IV1V of FIG- URE 3.

Briefly, the present invention provides a furnace construction having longitudinally extending parallel walls with periodic inwardly directed indentations in which support columns are disposed and shielded from the high furnace temperatures. Aflixed to the columns are support elements which extend through the indented portion of the furnace wall into the central interior portion of the furnace to support longitudinally extending parallel tubes. The support columns being located outside the furnace wall are arranged so that relatively cold air passes upwardly around them by convection to cool the columns. Since the support columns are maintained substantially cooler than the interior of the furnace the support elements which extend into the heated furnace are provided with a heat sink and consequently are maintained at less than operating temperatures.

Referring to the drawing there is shown in FIGURES 1 and 2 a tube-heating furnace composed of two parallel furnace compartments or chambers 1 and 2. The walls 3, composed of refractory material, are retained in a frame structure 20 and are terraced with sloping steps 4 and inclined wall surfaces 5 between adjacent steps.

Burners 6 are mounted in each of the steps 4 on both sides of the furnace chamber. Such a wall construction provides for zonal heat control and exceptional uniformity of heat within each zone. The top 7 of the furnace is enclosed conventionally with refractory material and a stack 8 extends upwardly to exhaust combustion gases. At spaced intervals along the furnace walls the terracing is broken by narrow indentations 9 where the wall projects inwardly to a point near the center of the chamber. The indentations along both sides of the furnace alternate with each other. Centrally located in each chamber are a number of horizontal furnace tubes 10 extending longitudinally through the furnace.

With reference to FIGURES 3 and 4, one of the narrow furnace wall indentations 9 is shown in greater detail. It may be readily observed that the furnace wall 3, including the wall portion surrounding the indentation 9, is composed of conventional refractory brick material within an exterior casing plate 11. Within each of the indentations is a carbon steel suport column 12 extending from the base of the furnace to the enclosed top portion. support elements 14 shown in FIGURES 3 and 4 are mounted in alignment with each of the furnace tubes 5 on the interior surface of the indented portion 9 of the furnace wall 3. Bolts 13 pass through the support column 12 and the furnace wall 3 to secure the support elements 14 in proper position to support the weight of the furnace tubes 5. The area outside the furnace wall 3 Within the indentations 9 is open to the atmosphere permitting cool air to be drawn upwardly by convection induced by the elevated temperature of the exterior surface of the walls to cool the support columns 12. Some of the heat to which the support elements 14 are exposed during operation of the furnace will be transmitted through the bolts 13 to the support columns 12 thus tending to cool and preserve the support elements 14 for a longer period of time than has been previously possible.

When the support elements 14 must be replaced because of their inevitable eventual deterioration only a minimum amount of shut-down time will be required. It will only be necessary to remove the bolts 13 from the exterior of the furnace thus releasing the support elements 14 after which new support elements may be placed in position and secured by new bolts inserted from outside the furnace. It is not necessary to in any way dislodge or remove the furnace tubes to peform this operation.

It may be readily observed that the present structure provides for furnace tube support columns which need not be produced from high temperature resistant, expensive steel alloys but may be produced from more common carbon steel and which need never be replaced since they are not exposed to the direct heat of the burners. Since the support columns are not subjected to the extremely high temperatures the problem of expansion and contraction is not as great thereby making it possible for the tubes to be supported at all times regardless of the furnace temperature. Furthermore, replacement of the individual support elements may be accomplished with minimum amount of shut-down time and without having to dislodge other parts of the furnace to perform this operation.

The above description and drawings are of the preferred embodiment of the invention, however, it will be apparent to those skilled in the art that alterations to the form of the apparatus disclosed may be made without departing from the spirit and scope of the invention. Such alternative embodiments, as well as the preferred embodiment, are intended to be within the scope of the following claims.

4- i What I claim is:

1. A tube furnace comprising a chamber including a pair of substantially parallel side Walls defining an elongated furnace radiant section, the furnace radiant section having a longitudinally extending chamber center line;

burner means heating said radiant section;

substantially horizontal tubes extending parallel to and between said side walls in proximity with said center line subjected to radiant heat in said chamber;

the side walls including a plurality of spaced vertically extending indentations alternately disposed lengthwise of the chamber projecting inwardly towards said tubes, the indentations having innermost surfaces close to the chamber center line;

means for supporting said tubes comprising a plurality of vertically extending support columns located within said indentations but exposed to ambient conditions whereby the support columns are shielded from high temperatures within said furnace, and individual supporting elements for each tube connected with said tubes extending through said innermost surfaces and secured to said support columns.

2. A tube furnace as claimed in claim 1 wherein the interior surfaces of said pair of side Walls between said indentations are identically terraced in the horizontal direction to produce horizontally extending separate heat ing zones.

3. A tube furnace as claimed in claim 1 wherein burners are located on the interior surfaces of said side walls to heat said tubes from opposite sides.

4. A tube furnace according to claim 1 wherein said support elements are secured to said support columns by means whereby they are readily removable from the support columns.

References Cited by the Examiner UNITED STATES PATENTS 2,105,821 1/1938 Parsons 122356 3,066,656 12/1962 Hensel l22-240 FOREIGN PATENTS 596,819 4/1960 Canada.

KENNETH W. SPRAGUE, Primary Examiner. 

1. A TUBE FURNACE COMPRISING A CHAMBER INCLUDING A PAIR OF SUBSTANTIALLY PARALLEL SIDE WALLS DEFINING AN ELONGATED FURNACE RADIANT SECTION, THE FURNACE RADIANT SECTION HAVING A LONGITUDINALLY EXTENDING CHAMBER CENTER LINE; BURNER MEANS HEATING SAID RADIANT SECTION; SUBSTANTIALLY HORIZONTAL TUBES EXTENDING PARALLEL TO AND BETWEEN SAID SIDE WALLS IN PROXIMITY WITH SAID CENTER LINE SUBJECTED TO RADIANT HEAT IN SAID CHAMBER; THE SIDE WALLS INCLUDING A PLURALITY OF SPACED VERTICALLY EXTENDING INDENTATIONS ALTERNATELY DISPOSED LENGTHWISE OF THE CHAMBER PROJECTING INWARDLY TOWARDS SAID TUBES, THE INDENTATIONS HAVING INNERMOST SURFACES CLOSE TO THE CHAMBER CENTER LINE; MEANS FOR SUPPORTING SAID TUBES COMPRISING A PLURALITY OF VERTICALLY EXTENDING SUPPORT COLUMNS LOCATED WITHIN SAID INDENTATIONS BUT EXPOSED TO AMBIENT CONDITIONS WHEREBY THE SUPPORT COLUMNS ARE SHIELDED FROM HIGH TEMPERATURES WITHIN SAID FURNACE, AND INDIVID- 